The present invention relates to novel polyolefin compositions having improved paintability. More particularly, the invention relates to blends comprising a major proportion of ethylene-propylene terpolymer and a minor proportion of a graft polymer which exhibit improved paintability. The graft polymer is selected from polymers of a vinyl aromatic hydrocarbon and at least one additional monomer selected from acrylonitrile, methacrylonitrile, and methylmethacrylate polymerized in the presence of a rubbery diene substrate. Still more particularly, the invention relates to blend compositions comprising 60% or more by weight ethylene-propylene diene monomer terpolymer (EPDM) and correspondingly 40% or less by weight graft polymer selected from the group acrylonitrile-butadiene-styrene (ABS), methylmethacrylate-butadiene-styrene (MBS) and methylmethacrylate-acrylonitrile-butadiene-styrene (MABS), which exhibit improved paintability, characterized in that adhesion of paint to these novel blend compositions is markedly improved over the EPDM terpolymer.
The use of EPDM olefin polymers in, for example, automotive applications, particularly where resiliency and/or impact resistance is required, has been limited by the poor paintability characteristics of these materials. Considerable research has been directed to overcoming this deficiency, and methods such as incorporation of low molecular weight polar compounds, surface activation by oxidizing or etching solutions and even treatment of the surfaces with flame, arcs or plasma spray techniques have been developed. While some improvement has resulted, particularly where surface treatments are employed, the more successful require multiple step treatments of the molded part to prepare the article for painting. Thus a composition capable of being molded to give parts having good paint adhesion characteristics without requiring added processing treatments would be a useful advance in the art.